In general, ultrasonic diagnostic apparatuses transmit ultrasound waves to an object such as a human or animal and detect echo signals reflected from the object, thereby displaying a tomographic image of a tissue inside the object on a monitor and providing to information necessary for diagnosis of the object. By performing the above process, the ultrasonic diagnostic apparatuses have been used for medical purposes such as detecting foreign substances within a living organism, assessing injuries, monitoring a tumor, and observing a fetus.
Ultrasound may be classified mainly into focused ultrasound and plane-wave is ultrasound. Focused ultrasound has the advantage of providing high resolution imaging but requires a large number of transmissions. On the other hand, plane-wave ultrasound is advantageous in acquiring an ultrasound image of a large area with a relatively small number of transmissions. Furthermore, the use of plane-wave ultrasound allows relatively simple calculation of a focusing delay for focus synthesis.
However, an ultrasound image acquired using plane-wave ultrasound may show a higher clutter level than when using focused ultrasound. As the clutter level of an ultrasound image increases, the contrast resolution of the ultrasound image may be degraded.